Just how popular are the UK's political blogs? Judging by the response to a Westmonster post, they do very well when talking about themselves - all usual blogging fayre, really.

An "esoteric post" about blog stats turned out to be the biggest ever story for Westmonster.com, and has everyone who cares huffing and puffing about the ins and outs of web statistics and - shocker - whether Iain Dale and Guido Fawkes have been inadvertently inflating their traffic figures. (I'll disclaim that Westmonster is published by Lloyd Shepherd, formerly of the Guardian parish although that was before my time. Actually Westmonster is published Messy Media, of which Shepherd is a co-managing director, just to be clear...)

This was all started by Tim Ireland, who spotted an error in the figures Guido was gleaning from his Google Analytics charts. And Iain Dale, too, had been claiming the number of visits was the number of visitors which, in the shortest definition I can muster, doesn't de-duplicate the number of visitors.

"An absolute unique is someone who visits the blog at least once a month (ie 53,255). A unique visitor is someone who visits the blog at least once a day - these are then amalgamated to get the monthly total of 239,368."

Come again? I think Dale has his cookies in a twist.

Being extremely inclined towards the obsessive when it comes to anything web statistical, I was amused at this rookie mistake by two of the big blog cheeses. The thing about web statistics is that the closer you look, the more complicated things get. It generally leads to a headache.

Uniques are the number of individual users that access a site in a month. If you visit again from, your second visit won't count because the server will recognise your computer's IP address and discount any subsequent visit during the month. So uniques are a pretty sound measure of the number of users a site has.

But...

If you deleter any cookies, or use a different computer, you would be counted again. Theoretically, if every user of a site accessed at home and work in a month, the site's unique user figure would actually be double what it might claim to be.

Yahoo, says Westmonster's Lloyd Shepherd, even divides its unique user figure by a seemingly random 2.5 to try and compensate for that. Dale and Guido Fawkes could both have user numbers well under the figure they claim: Dale, for example, claims he had 239,638 visitors for March, but analytics show 53,255 users - on Yahoo's calculations, that is actually more like 21,302.

Anyone claiming the number of de-duplicated visits to a site is the same as users is, at best, a little confused. At worst, it's misleading the readers and also the paying advertisers that expect accountable and accurate information on exactly what they are spending their money on.

Aspirin, anyone?

Update: I just got some stats from comScore on the political blogs most visited by people in the UK. The blogs still aren't on comScore's radar, but there some interesting points in the top ten sites from February this year.